Effects of supplemental chromium on interferon-gamma (IFN-γ) mRNA expression in response to Newcastle disease vaccine in broiler chicken

We report the effects of supplemental chromium (Cr) on interferon-gamma (IFN-γ) expression in response to Newcastle disease virus (NDV) vaccine in broiler chicken. Two hundred and eighty day old straight run broiler chicks were randomly selected and allocated at random to one of the seven treatment groups replicated four times having 10 chicks in each replication. Treatment 1 (C) was a standard control diet in which no Cr was offered to birds either through feed or drinking water. In treatments 2–4 (F500, F1000 and F1500), Cr in the form of chromium picolinate (CrPic) was added at rates of 500, 1000 and 1500 ppb in diets, respectively. In treatments 5–7 (W250, W500 and W750), Cr as added to the drinking water at rates of 250, 500 and 750 ppb, respectively. The feeding was continued from 1 to 49 d of age. On 49 d, three birds from each replicate, i.e. 12 birds/treatment were inoculated intramuscularly with R2B strain of NDV. Twelve unvaccinated birds along with 12 vaccinated birds from each treatment (four birds each day) were then sacrificed on 1, 3 and 7 days post-immunization to study the IFN-γ expression using quantitative real time PCR. Following the immunization, the IFN-γ mRNA expression in spleen was significantly (P < 0.01) either up-regulated or down-regulated at day 1 and day 3 post-stimulation. Whereas, IFN-γ mRNA expression reached basal level in all the vaccinated groups at day 7 post-stimulation. IFN-γ mRNA expression on day 1 was approximately two and four times higher than the control (C) levels in F500 and W500 groups, respectively. On 3 day post-immunization, IFN-γ mRNA expression in spleen was about 40 and 27 times higher than controls (C) in F500 and W500 groups, respectively. Other groups (F1000, F1500, W250 and W750) showed down-regulation of IFN-γ mRNA expression. The results suggested that the dosage of chromium modulates the expression of IFN-γ and route has effect on the onset and duration of the response. Thus, the supplementation of chromium at appropriate dose might be helpful to enhance the IFN-γ mRNA expression in response to NDV.